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| author | Mahesh Bandewar <maheshb@google.com> | 2024-09-04 16:13:05 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2024-09-08 19:40:33 +0200 |
| commit | c259acab839e57eab0318f32da4ae803a8d59397 (patch) | |
| tree | 2d04bad4ad9273e95fc0bd221bd70ec91ac3d3cd /drivers/ptp | |
| parent | net: sched: consistently use rcu_replace_pointer() in taprio_change() (diff) | |
| download | linux-c259acab839e57eab0318f32da4ae803a8d59397.tar.xz linux-c259acab839e57eab0318f32da4ae803a8d59397.zip | |
ptp/ioctl: support MONOTONIC{,_RAW} timestamps for PTP_SYS_OFFSET_EXTENDED
The ability to read the PHC (Physical Hardware Clock) alongside
multiple system clocks is currently dependent on the specific
hardware architecture. This limitation restricts the use of
PTP_SYS_OFFSET_PRECISE to certain hardware configurations.
The generic soultion which would work across all architectures
is to read the PHC along with the latency to perform PHC-read as
offered by PTP_SYS_OFFSET_EXTENDED which provides pre and post
timestamps. However, these timestamps are currently limited
to the CLOCK_REALTIME timebase. Since CLOCK_REALTIME is affected
by NTP (or similar time synchronization services), it can
experience significant jumps forward or backward. This hinders
the precise latency measurements that PTP_SYS_OFFSET_EXTENDED
is designed to provide.
This problem could be addressed by supporting MONOTONIC_RAW
timestamps within PTP_SYS_OFFSET_EXTENDED. Unlike CLOCK_REALTIME
or CLOCK_MONOTONIC, the MONOTONIC_RAW timebase is unaffected
by NTP adjustments.
This enhancement can be implemented by utilizing one of the three
reserved words within the PTP_SYS_OFFSET_EXTENDED struct to pass
the clock-id for timestamps. The current behavior aligns with
clock-id for CLOCK_REALTIME timebase (value of 0), ensuring
backward compatibility of the UAPI.
Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/ptp')
| -rw-r--r-- | drivers/ptp/ptp_chardev.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c index 2067b0120d08..ea96a14d72d1 100644 --- a/drivers/ptp/ptp_chardev.c +++ b/drivers/ptp/ptp_chardev.c @@ -359,11 +359,15 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd, extoff = NULL; break; } - if (extoff->n_samples > PTP_MAX_SAMPLES - || extoff->rsv[0] || extoff->rsv[1] || extoff->rsv[2]) { + if (extoff->n_samples > PTP_MAX_SAMPLES || + extoff->rsv[0] || extoff->rsv[1] || + (extoff->clockid != CLOCK_REALTIME && + extoff->clockid != CLOCK_MONOTONIC && + extoff->clockid != CLOCK_MONOTONIC_RAW)) { err = -EINVAL; break; } + sts.clockid = extoff->clockid; for (i = 0; i < extoff->n_samples; i++) { err = ptp->info->gettimex64(ptp->info, &ts, &sts); if (err) |